首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   127257篇
  免费   2360篇
  国内免费   443篇
化学   56411篇
晶体学   1015篇
力学   8192篇
数学   39035篇
物理学   25407篇
  2023年   384篇
  2022年   325篇
  2021年   540篇
  2020年   707篇
  2019年   680篇
  2018年   11094篇
  2017年   10758篇
  2016年   7430篇
  2015年   2278篇
  2014年   1750篇
  2013年   3363篇
  2012年   7182篇
  2011年   13684篇
  2010年   7612篇
  2009年   7636篇
  2008年   9418篇
  2007年   11494篇
  2006年   2974篇
  2005年   3957篇
  2004年   3798篇
  2003年   3777篇
  2002年   2593篇
  2001年   1217篇
  2000年   1105篇
  1999年   722篇
  1998年   624篇
  1997年   548篇
  1996年   694篇
  1995年   437篇
  1994年   460篇
  1993年   470篇
  1992年   463篇
  1991年   410篇
  1990年   382篇
  1989年   384篇
  1988年   325篇
  1987年   332篇
  1986年   290篇
  1985年   460篇
  1984年   415篇
  1983年   300篇
  1982年   393篇
  1981年   382篇
  1980年   344篇
  1979年   331篇
  1978年   314篇
  1976年   303篇
  1975年   275篇
  1974年   282篇
  1973年   288篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
By a result of Pigozzi and Kogalovskii, every algebraic latticeL having a completely join —irreducible top element can be represented as the lattice L() of equational theories extending some fixed theory . Conversely, strengthening a recent result due to Lampe, we show that such a representationL=L() forcesL to satisfy the following condition: if the top element ofL is the join of a nonempty subsetB ofL then there are elementsb..., B such thata=(... (((b1 a) b2) a) ... bn) a for alla L. In presence of modularity, this equation reduces to the identitya=(a b1) ... (a bn). Motivated by these facts, we study several weak forms of distributive laws in arbitrary lattices and related types of prime elements. The main tool for applications to universal algebra is a generalized version of Lampe's Zipper Lemma.Presented by Ralph Freese.  相似文献   
992.
LetO be the local ring of a irreducible algebroid curve and S its semigroup of values, Kunz in [7] proves thatO is a Gorenstein ring if and only if S is symmetrical. In this paper we give a generalization of this fact for the case of reduced curves with an arbitrary number of branches, d. For it we introduce a concept of symmetry for the semigroup of values S+ d which generalizes the well known symmetry for d=1 (i.e. the irreducible case). This concept of symmetry is also closely related to the symmetry introduced by García in [4] (for the d=2 case) and the author in [3] (for arbitrary d) with the main goal of the explicit determination of S (in the case of plane curves).  相似文献   
993.
994.
We prove that for the relative entropy of faithful normal states ? and ω on the von Neumann algebraM the formula $$S(\varphi ,\omega ) = \sup \{ \omega (h) - \log \varphi ^h (I):h = h^* \in M\}$$ holds.  相似文献   
995.
996.
This is our second paper devoted to the study of some non-linear Schrödinger equations with random potential. We study the non-linear eigenvalue problems corresponding to these equations. We exhibit a countable family of eigenfunctions corresponding to simple eigenvalues densely embedded in the band tails. Contrary to our results in the first paper, the results established in the present paper hold for an arbitrary strength of the non-linear (cubic) term in the non-linear Schrödinger equation.  相似文献   
997.
998.
999.
1000.
Using the reaction138Ba(α,2n)140Ce the magnetic moment of the 10 1 + isomer atE x =3714.7 keV in theN=82 nucleus140Ce has been determined by means of the TDPAD method toμ=+10.3(4)μ N . Measuredg-factors in140Ce are compared to calculations within the shell model with configuration mixing. For the 10 1 + isomer in140Ce the four proton configuration π(1g 7 2/2 ,2d 5 2/2 ) has been found to be dominant. From theg-factor measurement strong contributions of multiparticle excitations to thegp2d 3/2,π3s 1 2 or π1h 11 2 shells and admixtures of neutron excitations to the wave function of the 10 1 + state could be excluded. The strongE1γ-branch of the deexcitation of the 10 1 + isomer in140Ce can be explained by means of small admixtures of configurations which contain the outer subshell excitationsπ2f 7/2 andπ1h 9/2. On this basisE1 transitions experimentally observed in theN=82 nuclei140Ce,141Pr and145Eu may be understood.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号